How to view value of node output?
The Age output of the Particle Info node is measured in frames (like the particle setting itself). So the simplest way of normalizing the value (get it into 0..1 range) is to divide by the Life setting of the particle system:


You can also divide by the Lifetime output of Particle Info, giving the relative age for each particle:


Note however that the Lifetime value can vary for each particle depending on the Random factor in particle settings:

Divide by constant:



Divide by Lifetime (with Random = 0.75)